I've been learning French and German throughout the last years, and I tried different setups. I came to the conclusion that apps like duolingo lack a consistent (or any) narrative, following a set of characters that interact with each other and the world. A good example for German is Deutsche Welle: https://learngerman.dw.com/en/overview
I've recently written more on the topic in my post on linkedin: https://www.linkedin.com/pulse/why-duolingo-bad-way-learn-la...